Conventionally, styrenic resins, which excel in thermoforming capability and rigidity, have been used for containers of soft drinks, juices, specialty beverages/foods and the like. For example, Patent Document 1 proposes a styrenic resin sheet for such containers. On the other hand, in recent years, such containers have increasingly been produced in a series of steps including molding, filling of content and sealing of the lid. For example, Patent Document 2 proposes a multilayer resin sheet wherein a polystyrene resin layer and a polyolefin resin layer are laminated, preventing the generation of resin whiskers while punching in the process leading to the final product.
Additionally, multilayer resin sheets that are endowed with an oxygen barrier property by using a styrenic resin layer as the outermost layer and providing an ethylene-vinyl alcohol copolymer resin layer with an adhesive layer of a modified olefinic resin or the like interposed therebetween, thereby preventing loss of quality due to oxidation of the contents, and multilayer containers consisting thereof, have become common (Patent Document 3).
On the other hand, packaging materials for packaging contents such as food products have had problems in that the contents could adhere to the packaging material. The multilayer resin sheets formed by laminating a polystyrenic resin layer and a polyolefinic resin layer described above also have the problem of adhesion of food products to packaging materials such as containers using such sheets. Particularly in the case of containers for yogurt, the yogurt can often stick to the top edge portions of the container and splatter when the container is opened.
Patent Document 1: JP 2000-204210 A
Patent Document 2: JP 2006-21409 A
Patent Document 3: JP H11-58619 A